Flow angle sensor with image sensor

ABSTRACT

A flow angle sensor includes a sensing element, a background component connected to and movable with the sensing element, the background component having a marker, a lens adjacent the disk, an image sensor axially aligned with the lens, a light source positioned to illuminate the disk, and an image processing system connected to the image sensor. The image processing system provides an angle of attack output based on a location of the marker sensed by the image sensor.

BACKGROUND

The present disclosure relates to sensors, and in particular, to flowangle sensors.

Flow angle sensors, such as angle of attack sensors or side slip anglesensors, are installed on aircraft to generate air data parameters.Angle of attack sensors with rotatable vanes are installed on theexterior of an aircraft to measure the aircraft angle of attack, theangle between oncoming airflow and the aircraft zero line (a referenceline of the aircraft, such as a chord of a wing of the aircraft). Theangle of attack sensor is mounted to the aircraft such that therotatable vane protrudes outside the aircraft and is exposed to oncomingairflow. Aerodynamic forces acting on the rotatable vane cause the vaneto align with the direction of the oncoming airflow. Rotational positionof the vane is sensed and used to determine the aircraft angle ofattack. It can be difficult to measure the angle of attack under certainconditions.

SUMMARY

A flow angle sensor includes a sensing element, a background componentconnected to and movable with the sensing element, the backgroundcomponent having a marker, a lens adjacent the disk, an image sensoraxially aligned with the lens, a light source positioned to illuminatethe disk, and an image processing system connected to the image sensor.The image processing system provides an angle of attack output based ona location of the marker sensed by the image sensor.

An angle of attack sensor includes a housing, a faceplate positioned onthe housing, a vane assembly adjacent the faceplate, the vane assemblyincluding a vane connected to a vane shaft, a rotatable disk connectedto the vane shaft opposite the vane, the disk having a marker, a lensadjacent the disk, an image sensor axially aligned with the lens, alight source within the housing and positioned to illuminate the disk,and an image processing system connected to the image sensor.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of an angle of attack sensor.

FIG. 2 is a schematic view of the angle of attack sensor.

FIG. 3A is a schematic top view of a disk showing a marker.

FIG. 3B is a schematic top view of the disk showing the marker after thedisk has been rotated.

FIG. 4 is a schematic view of the angle of attack sensor showingvariables used for calculating angle of attack.

FIG. 5 is a schematic view showing movement of the marker along pixelsof an image sensor.

FIG. 6 is a flowchart showing a method for image processing.

FIG. 7 is a schematic view of an alternate embodiment of the angle ofattack sensor.

DETAILED DESCRIPTION

In general, the present disclosure describes an angle of attack sensorthat has an image sensor connected to an image processing system tomeasure angle of attack using optical sensing technology. The imagesensor determines the locations of a marker on a rotating disk connectedto a rotating vane by continuously capturing images of the marker usinga lens and a light source. The image processing system uses thelocations of the marker to determine the angular displacement of thevane and subsequently the local flow angle.

FIG. 1 is a perspective view of angle of attack sensor 10. Angle ofattack sensor 10 includes faceplate 12 (which includes mounting plate 14and chassis 16), housing 18, and vane assembly 20 (which includes vane24).

Angle of attack sensor 10 is a flow angle sensor. Faceplate 12 is amulti-piece faceplate that includes mounting plate 14 and chassis 16.Mounting plate 14 has an opening at a center of mounting plate 14.Chassis 16 is adjacent mounting plate 14 and may be heated. Mountingplate 14 is positioned on chassis 16 such that chassis 16 is locatedinward from or interior to mounting plate 14 with respect to housing 18.In alternate embodiments, faceplate may be a single-piece faceplate thatdoes not include chassis 16. Housing 18 is cylindrical with an annularsidewall between an open first end and a closed second end. In alternateembodiments, housing 18 may be any suitable shape. Faceplate 12 ispositioned on housing 18 adjacent to the open first end of housing 18.Mounting plate 14 is an outer piece of faceplate 12, and chassis 16 isan inner piece of faceplate 12. Vane assembly 20 is adjacent faceplate12. Vane assembly 20, which includes vane 24, has a portion that ispositioned in chassis 16 and extends through the opening of mountingplate 14. Vane 24 extends through mounting plate 14.

Angle of attack sensors 10 are installed on an aircraft and mounted tothe aircraft via fasteners, such as screws or bolts, and mounting holeson mounting plate 14. As a result, mounting plate 14 is about flush withthe skin of the aircraft and housing 18 extends within an interior ofthe aircraft. Vane 24 extends outside an exterior of aircraft and isexposed to external airflow, causing vane 24 to rotate with respect tomounting plate 14 and chassis 16 via a series of bearings within angleof attack sensor 10. Vane 24 rotates based on the local flow angle. Vane24 causes rotation of a vane shaft, and a disk within housing 18.Rotation of the rotatable vane is determined and used to measure theangle of attack. The measured angle of attack is communicated to aflight computer or other aircraft systems, such as avionics, air datainertial reference units (ADIRUs), flight control computers, or air datacomputers, and can be used to generate air data parameters related tothe aircraft flight condition.

FIG. 2 is a schematic view of angle of attack sensor 10. FIG. 3A is aschematic top view of disk 28 showing marker 30. FIG. 3B is a schematictop view of disk 28 showing marker 30 after disk 28 has been rotated.FIG. 4 is a schematic view of angle of attack sensor 10 showingvariables used for calculating angle of attack. FIG. 5 is a schematicview showing movement of marker 30 along pixels 40 of image sensor 34.FIG. 6 is a flowchart showing method 44 for image processing. FIGS. 2-6will be discussed together. Angle of attack sensor 10 includes faceplate12, housing 18, vane assembly 20 (which includes vane 24), vane shaft26, disk 28, marker 30, lens 32, image sensor 34, image processingsystem 36, and light source 38. Image sensor 34 includes pixels 40A-40N(“N” is used herein as an arbitrary integer), first marker location M1,second marker location M2, and pitch 42. Method 44 (shown in FIG. 6 )includes step 46, step 48, step 50, step 52, step 54, step 56, step 58,step 60, and step 62.

Faceplate 12 is positioned on housing 18. Vane assembly 20, whichincludes vane 24, extends through faceplate 12. Vane 24 projects intothe airstream that is aligned with the external airflow. Vane 24 is asensing element. An end of vane 24 may be positioned in an opening offaceplate 12. Vane 24 is connected to a first end of vane shaft 26. Vaneshaft 26 extends into housing 18. A second end of vane shaft 26 isinternally connected to rotating cylindrical disk 28. As such, vane 24is connected to disk 28 via vane shaft 26. Vane 24, vane shaft 26, anddisk 28 move, or rotate, together. Disk 28 is a background component formarker 30. Marker 30 is positioned in disk 28. Marker 30 may be a dot orany other suitable shape. Marker is in a fixed position within disk 28.As shown in FIGS. 3A and 3B, as disk 28 rotates, the location of marker30 changes. Lens 32 is adjacent disk 28. Lens 32 is a converging lens.Image sensor 34 is also placed along an axis of vane shaft 26 and isaxially aligned with disk 28 and lens 32. Image sensor 34 is acomplementary metal-oxide-semiconductor (CMOS) based image sensor. Inalternate embodiments, image sensor 34 may be any other suitable imagesensor chip or image sensor. Image processing system 36 is connected toimage sensor 34. Image processing system 36 may be electrically orwirelessly connected to image sensor 34. Light source 38 is withinhousing 18 and positioned to illuminate disk 28 for proper detection byimage sensor 34.

As seen in FIG. 4 , field of view FOV is equal to the diameter of disk28. In alternate embodiments, field of view FOV may be greater than orless than the diameter of disk 28 depending on desired resolution.Length X is the diagonal length of image sensor 34. Focal length f oflens 32 is the distance between lens 32 and image sensor 34. Workingdistance WD is the distance between disk 28 and lens 32. Focal length fand working distance WD determine the magnification for image processingsystem 36. Focal length f divided by working distance WD is equal tolength X divided by field of view FOV (f/WD=X/FOV). As such, field ofview FOV, length X of image sensor 34, focal length f, and workingdistance WD are variables used by image processing system 36 incalculating angle of attack.

As seen in FIG. 5 , image sensor 34 includes pixels 40A-40N. Imagesensor 34 has a two-dimensional fixed array of pixels 40A-40N. FIG. 5shows pixels 40A-40N. In alternate embodiments, image sensor 34 mayinclude any number of pixels. Pixels 40A-40N relate to the resolution ofimage sensor 34. First marker location M1 designates a first location ofmarker 30 determined from a first image of marker 30 within image sensor34. First marker location M1 corresponds to a first location of disk 28and vane 24. Second marker location M2 designates a second location ofmarker 30 determined from a second image of marker 30 within imagesensor 34. Second marker location M2 corresponds to a second location ofdisk 28 and vane 24. As marker 30 moves, images of marker 30 move amongpixels 40A-40N. Pitch 42 is the distance between first marker locationM1 and second marker location M2, or the distance between pixels 40A-40Ncorresponding to first marker location M1 and second marker location M2,on image sensor 34. As marker 30 rotates, it moves along an arc on imagesensor 34 to determine rotation of vane 24, resulting in movement in, ora change in position within, pixels 40 in both horizontal and vertical(or x-axis and y-axis) directions.

Disk 28 captures movement of vane 24. As vane 24 rotates, vane shaft 26and disk 28 rotate. Marker 30 is utilized for angle indication. Lightsource 38 illuminates disk 28 so that image sensor 34 can capture marker30 in disk 28 with the use of lens 32. Image sensor 34 captures theposition of marker 30. Image sensor 34 continuously senses the positionof marker 30 in disk 28 and transmits marker 30 position information toimage processing system 36. The location of marker 30 is used todetermine if and where marker 30 is moving within image sensor 34 tomeasure angular displacement of vane 24. As such, angle of attack sensor10 uses image processing system 36 to capture the movement of disk 28 bycalculating the angular movement of marker 30, which is directlyproportional to the angle of vane 24, based on tracking the position ofmarker 30 on images captured by image sensor 34 and calculating pitch42. Image processing system 36 uses the positions and number of pixels40A-40N occupied by marker 30 to calculate an angle of attack via animage processing algorithm.

For example, vane 24 begins in an initial position of zero degrees. Whenvane 24 is at zero degrees, an image of marker 30 is captured, and thelocation of marker 30 corresponds to first marker location M1. As such,first marker location M1 corresponds to a zero angle or defaultposition. As vane 24 rotates, the movement of circular disk 28 causesthe location of marker 30 to change from its default position. Imagesensor 34 captures a new image of marker 30 in a new location, whichcorresponds to second marker location M2. The change in position ofmarker 30, identified using second marker location M2 and the defaultposition, or first marker location M1, is equal to pitch 42, which isused to compute an angle via digital processing techniques. First markerlocation M1 and second marker location M2 may correspond to any twopositions of vane 24. First marker location M1 and second markerlocation M2 information is transmitted to image processing system 36,which uses an image processing algorithm that correlates the markerlocations M1, M2 to an aircraft angle of attack. For example, motion ofmarker 30 can be determined by the percentage of pixels 40 the image ofmarker 30 has moved across. As such, image processing system 36 providesan angle of attack output based on a location of marker 30 sensed byimage sensor 34.

FIG. 6 shows method 44 for image processing by image processing system36. Step 46 includes starting image capture. Image sensor 34 captures animage of marker 30 on disk 28. Step 48 includes image enhancement byremoving noise. Image processing system 36 receives the image capturedby image sensor 34. Image processing system 36 removes noise, therebyenhancing the image. Step 50 includes identifying marker 30 in thecaptured image. Image processing system 36 identifies marker 30 on theenhanced image. Step 52 includes locating marker 30 position usingdetails of pixels 40A-40N. Image processing system 36 locates theposition of marker 30 on the image. Step 54 includes identifying theangle of marker 30 based on the pixel number. Image processing system 36uses pixels 40A-40N to identify the angle of marker 30 by identifying inwhich of pixels 40A-40N image is located. Step 56 includes computing thecenter point in the image. Image processing system 36 determines thecenter point in the image of marker 30, generating first marker locationM1. Step 58 includes providing the angle value to image processingsystem 36. Image sensor 34 transmits information corresponding to thepixel 40 in which the center point of the image of marker 30 is locatedto image processing system 36. Step 60 includes capturing and storingthe position of marker 30. Image processing system 36 receives locationinformation from image sensor 34 and stores such information. Step 62includes capturing a new image in a predefined time. Image sensor 34captures a new image of marker 30 after a set amount of time todetermine whether marker 30 has moved. The new position of marker 30correlates to the angle at which vane 24 has moved. Method 44 iscontinuously repeated, with image sensor 34 constantly capturing imagesto track the position of marker 30 in corresponding pixels 40 todetermine corresponding movement of vane 24, which produces angle ofattack.

Traditional angle of attack sensors, or other flow angle sensors, useresolvers, rotatory variable differential transformers (RVDTs), andpotentiometer-based concepts for angle of attack measurement. As such,the sensor may rely on electromagnetics to measure local physicalangular displacement with respect to the air stream. Accuracy of theangle of attack measurement varies with temperature, and the sensingelement can cause increased friction, which is undesirable. For example,angle accuracy decreases with respect to temperature. Further, the angleis limited with RVDT and potentiometer-based systems of sensors,resulting in a limitation in measurement capabilities. The relativemeasurement of traditional systems is also dependent on mechanicalproperties of the vane shaft, such as friction, weight, and toleranceand additional gears that may be present in the system. Additionalexcitation is also required for the sensor, which cannot be completelyisolated from the system. Excitation connections through wires to thevane shaft and resolver or potentiometer are prone to electromagneticinterference (EMI). Changes in electrical parameters, like wireinductances and resistances, cause accuracy variations. As a result, anoffset error to the measured value needs to be corrected by calibration.Only relative measurement is possible, and losses will requirecalibration. Additionally, measured angle accuracy varies with angulardisplacement when using certain traditional technologies.

Because angle of attack sensor 10 does not require contact, friction andhysteresis are reduced, resulting in an increase in reliability andaccuracy of absolute angle of attack. The accuracy of angle of attacksensor 10 is less affected by temperature variations than traditionalsensors because only the image is monitored. Further, angle of attacksensor 10 is immune to EMI noise as angle of attack sensor 10 usesoptical image sensing and image processing to generate angle of attackmeasurements. Additionally, because angle of attack sensor 10 is anoptical-based system that does not require contact, angle of attacksensor 10 is less prone to effects of direct and indirect lightningstrike. Angle of attack sensor 10 is also capable of high-resolutionencoding. Angle of attack sensor 10 achieves the same high level ofaccuracy as traditional systems for the complete range of angulardisplacement. Increased magnification is balanced against decreasedfocal length f to result in a reasonably-sized angle of attack sensor 10with optimal angular resolution. As such, angle of attack sensor 10produces angle of attack measurements that are as accurate or moreaccurate than traditional angle of attack sensors.

FIG. 7 is a schematic view of angle of attack sensor 110. Angle ofattack sensor 110 includes faceplate 112, housing 118, and vane assembly120 (which includes vane 124), vane shaft 126, disk 128, marker 130,lens 132, image sensor 134, image processing system 136, light source138, and second location 139.

Angle of attack sensor 110 has the same structure and function asdescribed with respect to FIGS. 1-6 . However, angle of attack sensor110 has image processing system 136 positioned in second location 139rather than housing 118. Second location 139 is a location separate fromangle of attack sensor 110. Second location 139 may be the flightcontrols, another remote module, or any other suitable location. Imageprocessing system 136 in second location 139 is electrically orwirelessly connected to image sensor 134 of angle of attack sensor 110.Positioning image processing system 136 in second location 139 allowsangle of attack sensor 110 to have a smaller size.

While angle of attack sensors 10 and 110 have been described withrespect to rotatable vanes 24 and 124 as the sensing elements androtatable disks 28 and 128 as background components, angle of attacksensors with various types of sensing elements influenced by airflowexternal to the aircraft and various background components, includingthose that move side-to-side or up-and-down, (such as a flipper orcone-based system) can use image sensors (such as image sensors 34 and134), lenses (such as lenses 32 and 132), light sources (such as lightsources 38 and 138), and image processing systems (such as imageprocessing systems 36 and 136) to measure angle of attack via opticalsensing technology. Additionally, while such technology has beendescribed with respect to angle of attack sensor 10 and 110, it may alsobe used on other types of flow angle sensors, such as a side slipsensor.

Discussion of Possible Embodiments

The following are non-exclusive descriptions of possible embodiments ofthe present invention.

A flow angle sensor includes a sensing element; a background componentconnected to and movable with the sensing element, the backgroundcomponent having a marker; a lens adjacent the background component; animage sensor axially aligned with the lens; a light source positioned toilluminate the background component; and an image processing systemconnected to the image sensor, wherein the image processing systemprovides an angle of attack output based on a location of the markersensed by the image sensor.

The flow angle sensor of the preceding paragraph can optionally include,additionally and/or alternatively, any one or more of the followingfeatures, configurations and/or additional components:

The lens is a converging lens.

The image sensor is a CMOS based image sensor.

The flow angle sensor is an angle of attack sensor and the sensingelement is a vane of the angle of attack sensor.

The background component is a rotatable disk.

The vane is connected to the disk via a vane shaft connected to the vaneand the disk.

The distance between the lens and the image sensor divided by thedistance between the disk and the lens is equal to the length of theimage sensor divided by the field of view.

The image processing system is wirelessly connected to the image sensor.

The image sensor includes a two-dimensional fixed array of pixels.

The image sensor captures images of the marker to determine a firstlocation and a second location of the marker as a distance betweenpixels corresponding to the first location and the second location ofthe marker.

An angle of attack sensor includes a housing; a faceplate positioned onthe housing; a vane assembly adjacent the faceplate, the vane assemblyincluding a vane; a vane shaft connected to the vane; a rotatable diskconnected to the vane shaft opposite the vane, the disk having a marker;a lens adjacent the disk; an image sensor axially aligned with the lens;a light source within the housing and positioned to illuminate the disk;and an image processing system connected to the image sensor.

The angle of attack sensor of the preceding paragraph can optionallyinclude, additionally and/or alternatively, any one or more of thefollowing features, configurations and/or additional components:

The faceplate is a multi-piece faceplate including: a mounting platehaving an opening; and a chassis positioned adjacent the mounting plateand located inward from the mounting plate with respect to the housing.

The lens is a converging lens.

The image sensor is a CMOS based image sensor.

The image processing system is wirelessly connected to the image sensor.

The image processing system is electrically connected to the imagesensor.

The vane shaft, the rotating disk, the lens, the light source, and theimage sensor are positioned in a first location, the first locationbeing the housing of the angle of attack sensor, and the imageprocessing system is positioned in a second location.

The second location is flight controls of an aircraft.

The image processing system provides an angle of attack output based ona location of the marker sensed by the image sensor.

The image sensor captures images of the marker to determine a firstlocation and a second location of the marker and a change in position ofthe marker within pixels corresponding to the first location and thesecond location of the marker.

While the invention has been described with reference to an exemplaryembodiment(s), it will be understood by those skilled in the art thatvarious changes may be made and equivalents may be substituted forelements thereof without departing from the scope of the invention. Inaddition, many modifications may be made to adapt a particular situationor material to the teachings of the invention without departing from theessential scope thereof. Therefore, it is intended that the inventionnot be limited to the particular embodiment(s) disclosed, but that theinvention will include all embodiments falling within the scope of theappended claims.

1. A flow angle sensor comprising: a sensing element; a backgroundcomponent connected to and movable with the sensing element, thebackground component having a marker; a lens adjacent the backgroundcomponent; an image sensor axially aligned with the lens; a light sourcepositioned to illuminate the background component; and an imageprocessing system connected to the image sensor, wherein the imageprocessing system provides an angle of attack output based on a locationof the marker sensed by the image sensor.
 2. The flow angle sensor ofclaim 1, wherein the lens is a converging lens.
 3. The flow angle sensorof claim 1, wherein the image sensor is a CMOS based image sensor. 4.The flow angle sensor of claim 1, wherein the flow angle sensor is anangle of attack sensor and the sensing element is a vane of the angle ofattack sensor.
 5. The flow angle sensor of claim 4, wherein thebackground component is a rotatable disk.
 6. The flow angle sensor ofclaim 5, wherein the vane is connected to the disk via a vane shaftconnected to the vane and the disk.
 7. The flow angle sensor of claim 1,wherein the distance between the lens and the image sensor divided bythe distance between the disk and the lens is equal to the length of theimage sensor divided by the field of view.
 8. The flow angle sensor ofclaim 1, wherein the image processing system is wirelessly connected tothe image sensor.
 9. The flow angle sensor of claim 1, wherein the imagesensor includes a two-dimensional fixed array of pixels.
 10. The flowangle sensor of claim 9, wherein the image sensor captures images of themarker to determine a first location and a second location of the markeras a distance between pixels corresponding to the first location and thesecond location of the marker.
 11. An angle of attack sensor comprising:a housing; a faceplate positioned on the housing; a vane assemblyadjacent the faceplate, the vane assembly including a vane; a vane shaftconnected to the vane; a rotatable disk connected to the vane shaftopposite the vane, the disk having a marker; a lens adjacent the disk;an image sensor axially aligned with the lens; a light source within thehousing and positioned to illuminate the disk; and an image processingsystem connected to the image sensor.
 12. The angle of attack sensor ofclaim 11, wherein the faceplate is a multi-piece faceplate including: amounting plate having an opening; and a chassis positioned adjacent themounting plate and located inward from the mounting plate with respectto the housing.
 13. The angle of attack sensor of claim 11, wherein thelens is a converging lens.
 14. The angle of attack sensor of claim 13,wherein the image sensor is a CMOS based image sensor.
 15. The angle ofattack sensor of claim 14, wherein the image processing system iswirelessly connected to the image sensor.
 16. The angle of attack sensorof claim 14, wherein the image processing system is electricallyconnected to the image sensor.
 17. The angle of attack sensor of claim11, wherein the vane shaft, the rotating disk, the lens, the lightsource, and the image sensor are positioned in a first location, thefirst location being the housing of the angle of attack sensor, and theimage processing system is positioned in a second location.
 18. Theangle of attack sensor of claim 16, wherein the second location isflight controls of an aircraft.
 19. The angle of attack sensor of claim11, wherein the image processing system provides an angle of attackoutput based on a location of the marker sensed by the image sensor. 20.The angle of attack sensor of claim 19, wherein the image sensorcaptures images of the marker to determine a first location and a secondlocation of the marker and a change in position of the marker withinpixels corresponding to the first location and the second location ofthe marker.